Spinneret production



Jan. 23, 1962 J. s. COBB SPINNERET PRODUCTION Filed Nov. 26, 1958 FIG.4

3,017,780 Patented Jan. 23, 1962 33913789 SPINIJERET PRODUQTIQN James S. Cobb, Martinsville, Va, assignor to E. I. du Pont de Nernours and Company, Wilmington, Del., a corporation of Delaware Filed Nov. 26, 1958, Ser. No. 776,585 7 Claims. (Ci. 76-107) This invention relates generally to the extrusion of viscous organic materials and, more particularly, to the fabrication of a spinneret adapted for use in the spinning of synthetic filaments.

In the preparation of spinneret capillaries, the procedure of punching a straight round hole through the thickness of a blank remaining after the blank has been counterbored is known. The fabrication of slotted and irregular holes by a method in which a number of round holes are drilled in a line and in which the walls between the holes are removed by broaching is also known. These procedures are time-consuming and expensive, require additional finishing steps, and result in various imperfections such as drill rings and broach burrs in the Walls of the finished holes.

The most important object of the present invention is to present a method of fabricating spinneret holes having optimum flow characteristics.

Another object of the invention is the fabrication of slotted and other iregularly shaped holes by a method in which stamping and punching steps alone are involved and in which no drilling or broaching, as such, is necessary.

With these and other objects in view, the presently disclosed method comprises generally the steps of recessing a blank, stamping into the recess with a wedge-shaped punch tapered in the direction of its advance, removing the deformation or protuberance left on the face of the spinneret blank, and surface punching with a straight punch. The resulting hole is tapered through the major portion of its length and terminates in straight-walled portions and a precisely formed orifice.

In the drawings:

FIGURE 1 is an enlarged fragmentary perspective sec tion of a spinneret blank which has been stamped in accordance with the teachings of the present invention;

FIG. 2 is a sectional view similar to that shown in FIG. 1 after the excess punched-out material has been removed from the spinneret face;

FIG. 3 illustrates the manner in which the hole of FIG. 2 is sized and finished with a straight punch;

FIG. 4 is an enlarged fragmentary perspective section taken through the counterbore and finished hole of a spinneret made according to the invention; and

FIG. 5 shows the wedge-shaped punch used in starting the hole, as shown in FIG. 1.

Referring now to FIG. 1, the numeral designates the flat bottom of a counterbore which has been formed as by drilling, in a spinneret blank 12 as the first step in the preparation of a hole 14. In the practice of this invention, the blank 12 is counterbored to within about 0.012 inch from the spinneret face. After a plurality of such counterbores have been formed in the blank 12, each is stamped, using the tool illustrated in FIG. 5, to start the hole 14. During this stamping step, a soft metal back-up plate 16 is positioned between the blank 12 and the punch plate and prevents tearing out of the excess material or protuberance left on the face of the spinneret. It should be noted that the partially prepared hole 14 extends beyond the lower face 18 of the blank 12.

The next step in the production of the spinneret is to remove the excess material 15 from the lower face 18, by sanding or grinding, so as to present an undersized orifice 20, as shown in FIG. 2..

The next and final step is illustrated in FIG. 3 wherein it is seen that a straight punch 22 having the dimensions of the finished orifice is used to size and finish the hole. In this final step, the blank 12 is punched from the face 18 whereas the stamping step is made through the counterbore 10.

A finished hole is illustrated in FIG. 4, together with the counterbore which was formed initially to leave the thickness in which the hole is fabricated. The hole has straight wall sections 24 which result from the use of the surface punch 22 and which extend to tapered wall portions 2s. The hole merges with the bottom 10 of the counterbore in a rounded edge 28 which has a radius of about 0.012 inch and is formed as a result of the natural How of the spinneret metal during the stamping step. The finished hole also has angularly disposed 'end walls 30 which, along with wall portions 26, conform generally to the wedge shape of a punch 32.

The tapered wedge-shaped punch 32, as illustrated in FIG. 5, has an included angle equal to the desired angular dimensions of the hole and a rectangularly shaped tip 34 having dimensions substantially equal to those of the unfinished orifice 20 illustrated in FIG. 2. The included angle of the tapered punch, between the ends as well as the sides, should be between 20 and 40 since it has been found that, with an angle of less than 20, the punch breaks readily and, with an angle of over 40, an undesirable amount of material is punched through the blank, leaving an oversize orifice. An angle of about 30 is preferred.

In carrying out the process, the blank '12 is first counterbored, as indicated by the numeral 10, and then positioned on the soft metal back-up plate 16. In sequence, the remaining thickness of the blank is stamped with a tapered punch of the configuration shown in FIG. 5, removed from the die, and polished to remove the protuberance 15 raised on the spinneret face by the punch 32. The unfinished hole is as illustrated in FIG. 2. To finish the hole, the straight punch 22 shown in FIG. 3 is used from the face 18 of the spinneret to size the orifice and to form the straight wall portions 24, the height of each of which is approximately equal to the width of the finished orifice. Thus, a straight-walled, smooth hole is formed by the cutting action of the surface punch 22 in the tapered sec-tion previously formed by the stamping punch. In this finishing step, no burr formation results when the surface punch breaks out into the tapered section. Depending on the configuration desired, various shapes of punches may be used such as Y, cruciform, hexiform, and the like. The slot or slots of the configuration chosen have a length to width ratio of between 2:1 and 20:1, with the slot width being in the neighborhood of 0.002 inch.

Other advantages inherent in the practice of this invention will occur readily to those skilled in the art and, accordingly, its extent is intended to be limited only by the scope of the appended claims.

I claim:

1. In the production of s-pinnerets, the steps of: stamping a blind hole in one face of a blank with a punch tapered in the direction of its advance to produce a protuberance on the opposite face; polishing the protuberance from the blank to present an orifice; and finishing the hole and orifice by punching through said orifice, from said opposite face of the blank, with a straight punch having cross-sectional dimensions slightly greater than those of said orifice.

2. In the production of spinnerets, the steps of: stamping a tapered hole in one face of a metallic blank to present a protuberance on the opposite face; polishing the protuberance from the blank to present an orifice; and finishing the hole and orifice by punching through said orifice, from said opposite face, to present a straight wall portion in the tapered end of the hole.

3. In the production of spinnerets, the steps of: stamping a hole in one face of a metallic blank with a punch tapered in the direction of its advance and having an included angle of between 20 and 40 to produce a protuberance on the opposite face; polishing the protuberance from the blank to present an orifice at the tapered end of said hole; and finishing the hole and orifice by punching through the orifice, from said opposite face, with a straight punch having cross-sectional dimensions slightly greater than those of said orifice.

4. In the production of spinnerets, the steps of: drilling a flat bottom counterbore in one face of a metal blank; stamping said blank, through said counterbore, with a punch tapered in the direction of its advance to produce a tapered hole in said blank and a protuberance on its opposite face; polishing the protuberance from the blank to present an orifice at the tapered end of said hole; and finishing the hole and orifice by punching through the orifice, from said opposite face, with a straight punch having cross-sectional dimensions slightly greater than those of said orifice.

5. The process of claim 4 wherein said punches are rectangular in cross-section.

6. The process of claim 4 wherein said punches are Y-shaped in cross-section.

7. The process of claim 4 wherein said punches are cruciform in cross-section.

References Cited in the file of this patent UNITED STATES PATENTS 2,148,221 Schneider Feb. 21, 1939 2,211,946 Graves Aug. 20, 1940 2,341,555 Jones Feb. 15, 1944 2,618,989 Cupler Nov. 25, 1952 2,742,667 Clouzeau et al Apr. 24, 1956 

